METHOD FOR OPERATING AN ENGINE, ENGINE AND MOTOR VEHICLE

Description

[0001] The invention relates to a method for operating an internal combustion engine with a fuel tank system comprising a tank venting valve. The invention further relates to an internal combustion engine suitable for carrying out such a method and to a motor vehicle with such an internal combustion engine.

[0002] A fuel tank system for a motor vehicle's internal combustion engine typically includes a vent line that allows pressure buildup in the fuel tank, caused, for example, by fuel evaporating at high ambient temperatures, to be released into the environment. Due to emissions regulations, it is essential that no fuel vapors escape into the environment. This is achieved by integrating a fuel vapor filter, usually an activated carbon filter, into the vent line to absorb the fuel vapors.

[0003] To regenerate such a fuel vapor filter, the tank system is additionally equipped with a purge gas line, which is connected on one side to the fuel vapor filter and on the other to the fresh air / fuel mixture of the internal combustion engine. During operation of the internal combustion engine, ambient air can be drawn in through an ambient air inlet of the fuel vapor filter by means of a vacuum created at the point where the purge gas line connects to the fresh air / fuel mixture, compared to the ambient pressure. This air flows through the fuel vapor filter in the opposite direction to the flow direction of the fuel vapors from the fuel tank into the fuel vapor filter, thus purging it. The fuel vapors from the fuel vapor filter are then fed to the combustion chambers of the internal combustion engine via the fresh air / fuel mixture.

[0004] DE 44 01 887 A1 discloses a control of a purge gas flow in a purge gas line of a fuel tank system by means of a control valve based on the measurement signal of a lambda sensor integrated into the exhaust stream of an associated internal combustion engine.

[0005] DE 10 2011 086 946 A1 describes a turbocharged internal combustion engine with a fuel tank system that can be vented via two purge gas lines. A first purge gas line, incorporating a venting valve, leads into a section of the fresh gas line downstream of the compressor, and a second purge gas line, comprising a purge gas delivery device, leads into a section of the fresh gas line upstream of the compressor. The loading of a fuel vapor filter in the tank system is determined based on the measurement signal of a lambda sensor.

[0006] EP 3 354 508 A1 discloses a method for regenerating a sorption storage tank of a fuel system of an internal combustion engine comprising the following steps: Detecting an operating state of the internal combustion engine; controlling a purge air pump and adjusting the purge air flow according to an operating state of an internal combustion engine and / or a compressor of the internal combustion engine; regenerating the fuel from the sorption storage; metering the regenerated fuel via the purge air flow into the intake air flow that is directed to the internal combustion engine. where the adjustment of the purge air flow and metering of the regenerated fuel is carried out taking into account one of the following parameters: λ value, purge air pressure, purge air volume flow, purge air temperature.

[0007] DE 10 2015 216 504 A1 discloses a method for venting a fuel tank system of an internal combustion engine, comprising a fuel tank, a fuel vapor filter in fluid-conducting communication with an ambient outlet, a vent line leading from the fuel tank to the fuel vapor filter, a purge gas line leading from the fuel vapor filter to a fresh gas stream of the internal combustion engine, and a purge gas conveying device integrated into the purge gas line, wherein the internal combustion engine further comprises an exhaust stream with an integrated lambda sensor. The method provides that, in a first stage of tank venting after a cold start of the internal combustion engine, fuel vapors are conveyed from the fuel tank by means of the purge gas conveying device while a vent valve integrated into the vent line is held closed.Therefore, in this first phase, only fuel vapors, and no air, are conveyed through the purge gas line. Only when a certain vacuum threshold in the fuel tank is reached is the vent valve opened, and then the fuel vapor filter is regenerated using air drawn in through the vent line. During this first phase, the lambda sensor can be used to determine the hydrocarbon (HC) concentration of the fuel vapors flowing through the purge gas line, in order to adjust the speed of the purge gas delivery device and thus the flow rate in the purge gas line.

[0008] EP 2 627 889 A1 and WO 2012 / 049219 A1 disclose a method and a device for operating a tank venting system with a purge air valve integrated into a purge air line.

[0009] WO 2012 / 049230 A1 describes an internal combustion engine with a tank venting system in which an HC sensor is arranged in a purge gas line to determine the hydrocarbon content of a gas stream. Furthermore, a measuring device, for example a lambda probe, is integrated into an exhaust stream of the internal combustion engine. This device determines an exhaust gas parameter, compares it with a predetermined target value, and, if a limit value of the difference is exceeded, triggers a test to determine whether the HC sensor is malfunctioning.

[0010] The invention was based on the objective of providing an advantageous method for venting a fuel tank system of an internal combustion engine.

[0011] This problem is solved by means of a method according to claim 1. An internal combustion engine suitable for carrying out such a method is the subject of claim 3. Advantageous embodiments of the method according to the invention and preferred configurations of the internal combustion engine according to the invention are the subject of further claims and / or will become apparent from the following description of the invention.

[0012] According to the invention, a method for venting a fuel tank system of an internal combustion engine is provided, wherein the fuel tank system at least a fuel tank, a fuel vapor filter in fluid-conducting communication with an ambient outlet, a vent line leading from the fuel tank to the fuel vapor filter, a purge gas line leading from the fuel vapor filter to a fresh gas stream of the internal combustion engine, a purge gas delivery device integrated into the purge gas line, i.e. a so-called purge gas pump, and a control valve integrated into the purge gas line (so-called tank vent valve). The internal combustion engine also features an exhaust system with an integrated lambda sensor. The purge gas delivery device is controlled based on the lambda sensor's measurement signal to regulate the purge gas flow rate in the purge gas line. Furthermore, the control valve is also controlled based on the lambda sensor's measurement signal to regulate the purge gas flow rate in the purge gas line and the flow rate of purge gas introduced into the fresh gas line.This allows for particularly precise metering of the amount of purge gas to be introduced into the fresh gas, which has a positive effect on achieving a defined fuel-oxygen ratio of the fuel-air mixture quantities introduced into the combustion chamber(s) of the internal combustion engine and can therefore lead to advantageous operation of the internal combustion engine with, in particular, the highest possible efficiency and the lowest possible pollutant emissions.

[0013] The purge gas supply device and the control valve are controlled for at least one, preferably each, of these components, taking into account the control value of the other component, thus enabling particularly advantageous control. It is provided that the purge gas supply device operates in several drive speed stages and the control valve is controlled within a control range (e.g., 0% to 100%). The system switches from a relatively small drive speed stage to a relatively large drive speed stage if, during operation of the purge gas supply device at the relatively small drive speed stage, a greater purge gas demand is detected despite maximum control of the control valve, or if a higher purge gas flow rate is required in the purge gas line.

[0014] According to the invention, the term "fuel vapor filter" does not imply that it must filter the volatile fuel in gaseous form. Rather, the fuel may already be (partially) condensed again during the filtration process.

[0015] An internal combustion engine according to the invention comprises, on the one hand, at least A preferably spark-ignition internal combustion engine (e.g., a gasoline engine), a fresh gas line for supplying fresh gas to the internal combustion engine, an exhaust gas line comprising a lambda sensor for removing exhaust gas from the internal combustion engine, and a fuel tank system comprising at least one fuel tank, a fuel vapor filter in fluid-conducting communication with an ambient outlet, a vent line leading from the fuel tank to the fuel vapor filter, a purge gas line leading from the fuel vapor filter to the fresh gas line of the internal combustion engine, a purge gas delivery device integrated into the purge gas line, and a control valve integrated into the purge gas line. Furthermore, an internal combustion engine according to the invention has a control device configured for the automated execution of a method according to the invention.

[0016] The method according to the invention can be carried out particularly advantageously in an internal combustion engine which, as is also preferably provided for an internal combustion engine according to the invention, additionally comprises a lambda controller, which is a device or a software-technical device which, based on the measurement signal of the lambda sensor, regulates the quantities of fuel introduced into the combustion chamber(s) of the internal combustion engine in such a way that, taking into account the oxygen also introduced into the combustion chambers via the fresh gas, a defined fuel-oxygen ratio, which in the case of a spark-ignition internal combustion engine is generally an approximately stoichiometric fuel-oxygen ratio, is set.Since such an internal combustion engine should already include a lambda probe for the operation of such a lambda controller, the method according to the invention enables the control of the venting of the fuel tank system of the internal combustion engine without additional sensors, which has an advantageous effect on the costs of manufacturing such an internal combustion engine.

[0017] According to a preferred embodiment of a method according to the invention, it can be provided that the absolute value of the measuring signal of the lambda sensor and / or a correction value derived from this absolute value for the lambda controller of the internal combustion engine is used to control the purge gas supply device and / or the control valve.

[0018] According to a preferred embodiment of an internal combustion engine according to the invention, it can include a pressure and / or temperature sensor integrated into the purge gas line. Such a pressure and / or temperature sensor can be used, in particular, for diagnostic purposes and / or for determining the concentration of hydrocarbons (HC) in the purge gas. By additionally considering the HC concentrations, it is possible to determine even more precisely the quantities of hydrocarbons introduced via the purge gas into the fresh gas stream and from there into the combustion chambers of the internal combustion engine. This, in turn, can be compensated for by appropriate control of the internal combustion engine, particularly with regard to fuel injected via the injection valves, in order to achieve the most advantageous operation of the internal combustion engine.

[0019] Furthermore, an internal combustion engine according to the invention can advantageously include a shut-off valve integrated into the purge gas line, by means of which the flow through the purge gas line can be influenced and, in particular, interrupted as required and in addition to the control valve. By means of such a shut-off valve, a rapid isolation of the purge gas line, and thus of the fuel tank system, from the fresh gas stream of the internal combustion engine can be achieved, particularly independently of the control valve.

[0020] An internal combustion engine according to the invention can, in particular, be part of a motor vehicle. The combustion engine of the internal combustion engine can, in particular, be provided for the direct or indirect provision of drive power to the motor vehicle. The invention therefore further relates to a motor vehicle, in particular a wheeled and not rail-bound motor vehicle (preferably a passenger car or a truck), with an internal combustion engine according to the invention.

[0021] The indefinite articles ("ein", "eine", "einer" and "eines"), particularly in the patent claims and in the description generally explaining the patent claims, are to be understood as such and not as numerals. Accordingly, components specified by these articles are to be understood as existing at least once and potentially existing multiple times.

[0022] The present invention is explained in more detail below with reference to an embodiment illustrated in the drawings. The drawings show: Fig. 1: schematic representation of an internal combustion engine according to a first embodiment of the invention; Fig. 2: block diagram to illustrate the implementation of a method according to the invention based on the internal combustion engine according to the Fig. 1 ; and Fig. 3: a schematic representation of an internal combustion engine according to the invention in a second embodiment;

[0023] The Fig. 1Figure 1 shows an internal combustion engine according to the invention for a motor vehicle with a fuel tank system. This system comprises a fuel tank 10, which is connected via a vent line 12 to a fuel vapor filter 14, which may in particular be in the form of an activated carbon filter or at least include one. The fuel vapor filter 14 is further connected via a purge gas line 16 to a fresh gas stream 18 of the internal combustion engine, the purge gas line 16 opening into the fresh gas stream 18 upstream (with respect to the flow direction of fresh gas in the fresh gas stream 18 towards an internal combustion engine 20 of the internal combustion engine) of a charge air compressor 22 integrated into the fresh gas stream 18. The charge air compressor 22 is part of an exhaust gas turbocharger, which further comprises an exhaust gas turbine 24 integrated into an exhaust stream 26 of the internal combustion engine.In the charge air section of the fresh gas line 18 located between the charge air compressor 22 and the combustion engine 20, a throttle valve 36 is provided, which divides the charge air section into an upstream section, often referred to as the pressure pipe, and a downstream section, often referred to as the intake pipe.

[0024] In the operation of the internal combustion engine, mixtures consisting of fresh gas, which is entirely or mainly ambient air and is drawn in from the environment via an air filter 52, and fuel injected directly into the combustion chambers 28, for example by means of injection valves (not shown), are combusted in a known manner and in a defined sequence in combustion chambers 28 of the internal combustion engine 20, which are partially delimited by cylinders 30 of the internal combustion engine 20. The resulting pressure increases in the combustion chambers 28 are used to move pistons 32, which are guided to move longitudinally in the cylinders 30. These movements of the pistons 32 are converted into a rotary movement of a crankshaft (not shown) via connecting rods (not shown), whereby the guidance of the pistons 32 by the connecting rods via the crankshaft simultaneously results in a cyclic reciprocating movement of the pistons 32.The exhaust gas produced during the combustion of the fresh gas-fuel mixture in the combustion chambers 28 is discharged via the exhaust system 26 and flows through the exhaust turbine 24, which causes a turbine impeller (not shown) to rotate. This rotation of the turbine impeller is transmitted by means of a shaft 34 to a compressor impeller (not shown) of the charge air compressor 22, whereby the charge air compressor 22 compresses the fresh gas supplied to the combustion engine 20 via the fresh gas line 18.

[0025] The fuel vapor filter 14 of the fuel tank system is in gas-conducting contact with the environment via an ambient air line 38 on the side facing away from the vent line 12 and the purge gas line 16 (with regard to its filtering effect for fuel vapors), for which purpose the ambient air line 38 forms an ambient opening 44.

[0026] Fuel tank 10 is partially filled with fuel, some of which is normally liquid and has usually evaporated, so that fuel in fuel tank 10 is also present in a gaseous state. Such evaporation of fuel in fuel tank 10 is intensified by a relatively high fuel temperature, which can occur particularly at relatively high ambient temperatures and when there is a change in ambient pressure, for example, as a result of a vehicle with an internal combustion engine driving uphill.In order to avoid an impermissibly high overpressure in the fuel tank 10 caused by such evaporation, the possibility of pressure equalization with the ambient pressure is provided via the vent line 12 and the fuel vapor filter 14 as well as via the ambient air line 38, whereby the fuel vapor filter 14 prevents such pressure equalization from leading to the escape of fuel vapors into the environment.

[0027] Such venting of the fuel tank 10 leads to an increasing saturation of the fuel vapor filter 14, which in turn necessitates its regeneration at regular intervals. For this purpose, the fuel vapor filter 14 is purged by drawing in ambient air via the ambient air inlet 44 and the ambient air line 38. This ambient air flows through the fuel vapor filter 14 in the opposite direction to the flow during venting of the fuel tank 10, causing fuel molecules absorbed in the fuel vapor filter 14 to be carried away by the ambient air and introduced into the fresh gas stream 18 via the purge gas line 16. This fuel, which typically comprises a mixture of different hydrocarbons, is then supplied for combustion in the combustion chambers 28 of the internal combustion engine 20.

[0028] Such purging of the fuel vapor filter 14 is only intended to occur temporarily and always during the operation of the combustion engine 20, because only then can the fuel introduced into the fresh gas line 18 by purging the fuel vapor filter 14 be reliably supplied for combustion in the combustion chambers 34. Introducing fuel into the fresh gas line 18 when the combustion engine 26 is not in operation could, on the other hand, lead to the gaseous fuel escaping into the environment through leaks in the fresh gas line 18, and in particular through an intake opening of the fresh gas line 18.

[0029] A control or tank venting valve 42 is integrated into the purge gas line 16, which is arranged as close as possible to the outlet 40 of the purge gas line 16 into the fresh gas line 18 or is integrated into it.

[0030] For purging the fuel vapor filter 14, a sufficient pressure differential is required between the ambient pressure on the one hand and the pressure in the fresh gas line 18 in the region of the outlet 40 of the purge gas line 16 on the other. This differential is not always present due to strongly fluctuating pressures in the fresh gas line 18 during operation of the internal combustion engine 20. During operation of the internal combustion engine 20 and thus of the charge air compressor 22, the pressure of the fresh gas in the section of the fresh gas line 18 in the region of the outlet 40 of the purge gas line 16 is usually so low that a sufficient pressure differential exists compared to the ambient pressure at the outlet 44. However, this is not always the case.

[0031] To enable the fuel vapor filter 14 to be purged at any time, thus reliably preventing its complete saturation, the fuel tank system of the internal combustion engine includes a purge gas supply device 46 integrated into the purge gas line 16. This device is also commonly referred to as a "purge air pump" and can be designed as a piston compressor, particularly a vane compressor, or as a radial blower. By operating this purge gas supply device 46, ambient air can be actively drawn in through the ambient air outlet 44. This air then flows through the fuel vapor filter 14 for purging and is conveyed via the purge gas supply device 46 and the at least partially open tank vent valve 42 to the outlet 40 of the purge gas line 16.Furthermore, a shut-off valve 54, which has two switching positions, is integrated into the purge gas line 16 in a section between the fuel vapor filter 14 and the purge gas supply device 46. In a first switching position, the flow through the purge gas line 16 via the shut-off valve 54 is completely prevented, while in the second switching position, it allows such flow as much as possible.

[0032] At least the purge gas supply device 46, the tank vent valve 42, the shut-off valve 54, the throttle valve 36, and the injection valves can be controlled by a control device 48 (e.g., the engine control unit of the internal combustion engine). Simultaneously, the control device 48 receives measurement signals from a pressure sensor 50 integrated into the purge gas line 16 in a section between the purge gas supply device 46 and the tank vent valve 42, as well as from a lambda sensor 56 integrated into the exhaust stream 26 downstream of the exhaust turbine 24. The control device 48 also serves as a lambda controller for the internal combustion engine, determining the quantities of fuel to be injected into the combustion chambers 28 such that, during operation, a defined, possibly varying, fuel-oxygen ratio of the fuel-air mixture quantities burned in the combustion chambers 28 is maintained as precisely as possible.

[0033] The Fig. 2The functional relationships in the implementation of a method according to the invention for venting the fuel tank system of the internal combustion engine are illustrated in a block diagram. Fig. 1 .

[0034] In the Fig. 2The figure shows that exhaust gas produced during the combustion of the fuel-air mixture in the combustion chambers 28 of the internal combustion engine 20 flows around the lambda sensor 56 integrated into the exhaust stream 26, which then generates a measurement signal that represents the proportion of residual oxygen in the exhaust gas. This measurement signal is transmitted to the control device 48, which uses it both in its function as a lambda controller 48a and in its function as a control device 48b for tank venting and for controlling the purge gas delivery device 46, the tank venting valve 42, and the shut-off valve 54.It can be provided that the control device 48, in its function as a control device 48b for tank venting, uses both the absolute value of the measurement signal from the lambda sensor 56 and a correction value determined by the control device 48, in its function as a lambda controller 48a, to control the injection valves and the throttle valve 36 in a new or modified form based on the measurement signal from the lambda sensor 56, in order to maintain a defined fuel-oxygen ratio of the fuel-fresh gas mixture quantities that are burned in the combustion chambers 28. Based on these input variables, the control device 48, in its function as a control device 48b for tank venting, calculates control signals for the purge gas delivery device 46 and the tank venting valve 42.By appropriately actuating the purge gas supply device 46 and adjusting the tank vent valve 42, the quantity of purge gas introduced into the fresh gas stream 18 is influenced, which in turn affects the total amount of fuel introduced into the combustion chambers 28, i.e., via the injection valves on the one hand and the fresh gas on the other. The purge gas supply device 46 and the tank vent valve 42 are controlled by taking into account the control value of the other component.

[0035] In the case of the internal combustion engine according to the Fig. 3 Besides the purge gas supply device 46, only a tank venting valve 42 is integrated into the purge gas line 16. In contrast to the internal combustion engine according to the Fig. 1Therefore, no pressure and temperature sensor 50 and no shut-off valve 54 are provided. The functional relationships in carrying out a method according to the invention based on such an internal combustion engine according to the Fig. 3 can those of Fig. 2 are equivalent to. REFERENCE MARK LIST

[0036] 10 Fuel tank 12 Vent line 14 Fuel vapor filter 16 Purge gas line 18 Fresh gas train 20 Internal combustion engine 22 Charge air compressor 24 Exhaust turbine 26 Exhaust train 28 Combustion chamber of the internal combustion engine 30 Cylinder of the internal combustion engine 32 Piston of the internal combustion engine 34 Shaft 36 Throttle valve 38 Ambient air line 40 Purge gas line outlet 42 Control valve / Tank vent valve 44 Ambient outlet 46 Purge gas delivery device 48 Control device 48a Function of the control device as lambda controller 48b Function of the control device as a control device for tank venting 50 Pressure sensor 52 Air filter 54 Shut-off valve 56 Lambda probe

Claims

1. Method for venting a fuel tank system of an internal combustion engine having - a fuel tank (10), - a fuel vapor filter (14) fluidically connected to a surroundings opening (44), - a vent line (12) leading from the fuel tank (10) to the fuel vapor filter (14), - a purge gas line (16) leading from the fuel vapor filter (14) to a fresh gas tract (18) of the internal combustion engine, - a purge gas delivery device (46) integrated into the purge gas line (16) and - a closed-loop control valve (42) integrated into the purge gas line (16), the internal combustion engine further having an exhaust gas tract (26) comprising an integrated lambda probe (56), and the purge gas delivery device (46) being controlled on the basis of the measurement signal from the lambda sensor (56) in order to control, in a closed loop, a mass flow of the purge gas in the purge gas line (16), characterized in that the closed-loop control valve (42) is also controlled on the basis of the measurement signal from the lambda sensor (56) in order to control, in a closed loop, the mass flow of the purge gas in the purge gas line (16), at least one component out of the purge gas delivery device (46) and the closed-loop control valve (42) being controlled whilst taking into account the control value of the other component, it being possible for the purge gas delivery device (46) to be operated in a plurality of drive speed stages and for the closed-loop control valve (42) to be controlled in a control range, a change being made from operation of the purge gas delivery device (46) in a relatively small drive speed stage to operation in a relatively large drive speed stage if, during operation of the purge gas delivery device (46) in the relatively small drive speed stage, a greater purge gas requirement is detected despite a maximum control of the closed-loop control valve (42).

2. Method according to claim 1, characterized in that the absolute value of the measurement signal from the lambda sensor (56) and / or a correction value for a lambda controller (48b) of the internal combustion engine, which correction value is derived from said absolute value, is used in order to control the purge gas delivery device (46) and / or the closed-loop control valve (42).

3. Internal combustion engine, comprising - a combustion motor (20), - a fresh gas tract (18) for supplying fresh gas to the combustion motor (20), - an exhaust gas tract (26) for discharging exhaust gas from the combustion motor (20), which exhaust gas tract has a lambda probe, - a fuel tank system having - a fuel tank (10), - a fuel vapor filter (14) fluidically connected to a surroundings opening (44), - a vent line (12) leading from the fuel tank (10) to the fuel vapor filter (14), - a purge gas line (16) leading from the fuel vapor filter (14) to the fresh gas tract (18) of the internal combustion engine, - a purge gas delivery device (46) integrated into the purge gas line (16) and - a closed-loop control valve (42) integrated into the purge gas line (16), and comprising - an open-loop control device (48), characterized in that the open-loop control device (48) is designed to carry out a method according to any of the preceding claims in an automated manner.

4. Internal combustion engine according to claim 3, characterized by a pressure sensor and / or temperature sensor (50) integrated into the purge gas line (16).

5. Internal combustion engine according to either of claims 3 and 4, characterized by a shut-off valve (54) integrated into the purge gas line (16).